Petrol-fueled internal combustion engines normally comprise a throttle valve for regulating air flow to the cylinders. A throttle valve comprises a valve body housing a valve seat engaged by a throttle disk, which is fitted to a drive shaft and rotated between an open position and a closed position by an electric motor connected to the shaft by a gear transmission. One end of the drive shaft is fitted with a position sensor, which determines the angular position of the drive shaft (i.e. of the throttle disk) to permit feedback control of the electric motor by a control unit.
The position sensor comprises a rotor fitted to the drive shaft, and a stator facing the rotor to determine the angular position of the rotor, and may be a “contact” type (typically comprising a potentiometer), i.e. the rotor and stator are connected mechanically, or a “contactless” type, i.e. with no mechanical connection between the rotor and stator of the position sensor. One example of an inductive “contactless” position sensor commonly used to determine the angular position of the drive shaft of an electronically controlled throttle valve is described in U.S. Pat. No. 6,236,199B1.
The electric motor, the gear transmission, and the position sensor are housed inside a chamber housing the valve body, and which is closed by a removable cover normally made of plastic or metal material. The cover is fitted with an electric connector for connecting the throttle valve electrically to the internal combustion engine electric system; and an inner surface of the cover is fitted with a printed circuit supporting the position sensor stator and the electric connections between the position sensor and the electric connector and between the electric motor and the electric connector.
U.S. Pat. No. 5,672,818B1 describes one example of a throttle valve, in which the position sensor stator is fixed to the housing chamber cover.
Producing a cover of the type described above, however, is extremely complex, in that the cover must be airtight to prevent in-service contamination of the housing chamber by external agents, and must also ensure a high degree of precision in terms of planarity and position of the position sensor stator, to avoid position sensor reading errors.
U.S.2005155780 discloses a cover for a chamber of a housing of a throttle valve, said cover comprising an approximately plate-type carrier carrying a network of conductors which is embodied as a pressed screen and provided with a sensor.
U.S.2005106928 discloses a contact unit including a contact plate and a connection plug for an adjusting device; a position sensor is disposed on the contact plate whose electrical contact results over conductor tracks molded into the contact plate.